1990 running rough. Worse after long drive. Smells rich at idle.

[Spectre_240sx]

I've got a 1990 that is running fairly rough. It's better some days than others, but it seems pretty random. It seems worse after driving for a while as well. A while back it was really bad and I had to clean the contacts for the fuel injectors. It doesn't seem like the same issue now, though.

I'm thinking it's between the MAFS and the O2 sensor because it smells rich when it's at idle, but I'd rather not just start replacing parts and I don't want to screw with the MAFS if I can avoid it because I know it's very sensitive.

Any ideas?

[Spectre_240sx]

Update, just for the heck of it I took a look at the contacts for the MAFS and they look clean. Scraped them down a bit just to be sure, but it didn't change things at all.

It's definitely running rich. If I rev it while standing still I hear a lot of little backfires then one big backfire as it comes back down to idle. Besides a bad ECU, is there anything besides MAFS and O2 sensors that would make it run rich like that?